itch.io

Eh, the world mostly just evolved that way when I wrote it. People in this world really aren't anywhere near as horny as in IRL, so instead of having sex for fun, people primarily only have sex to procreate. Since there's hardly any sex for fun or relief, there's not nearly as much sex, straight or otherwise, going on in the world. On that note, porn, brothels, and prostitutes don't really exist much, if at all, either.
Like, I'm sure people are pairing off in same-sex couples every now and then, they're just not having sex with each other much.
(EDIT: almost forgot, a big part of why I made the world so sex-free is because all of humanity lives on a continent roughly the size of Texas. If they had the same libidos as we do IRL, they'd be overpopulated in a few decades, heh.)

That said, something about the hybrids biology just magnetizes them to sexual activity, and thanks to genetic drift caused by the ambient A-Energy found in the world, anyone that spends a lot of time around the hybrids, or anyone that lives too close to the lab tends to have a more active libido, so little by little, people who live in the ghetto (especially the people that work at the lab) are becoming more promiscuous, having  sex for fun, regardless of if it's with a hybrid or with each other.
Ironically, it's almost like a mirror of the outside world; on the outside, people don't have sex for fun, they're just having sex for procreation. On the inside, there's a strong incentive NOT to have kids (why would someone have kids in an enclosed city where they can never leave?), so it's a bit flipped, they have sex for fun, but not for procreation.

The MC not having a libido or any physical attraction to anyone, I guess I did that for a few reasons, like wanting to keep the character's gender and bodytype fairly ambiguous so pretty much anyone can self-insert or imagine them however they want, and also because there's already so many games out there where you just go around screwing everyone you meet (not that there's anything wrong with that.)
It also gives the hybrids someone a bit grounded to lean on, and allows me to write a wider variety of types of scenes; also it comes with the added bonus that I don't have to worry about too much romantic drama, as the MC stays out of most of that, heh.

Anywho, if anyone ever wants more lore or other random factoids, they're welcome to ask, this world's pretty complicated, if a bit small.